Moose eat hearty in the flush days of summer, and depend on their stores of fat and protein to get them through Alaska's lean winters. Because nutrition is such an important part of moose biology, much of the work at Alaska's Kenai Moose Research Center looks at metabolism and diet.
Just as medical doctors use ultrasound to look at a patient's internal organs, ultrasound technology allows moose researcher John Crouse to measure the layer of fat on a moose to gauge the condition of the animal.
"An ultrasound can be a real good index of body condition," he said. "Going into winter, if a moose hits 17 percent body fat, that's pretty good shape. Some are at 28 percent; some are as low as 3 percent - that's a hurting unit, about ready to keel over. Anyone over 25 percent is a fat animal in good shape for the winter."
How nutrition is related to reproduction is an important area of moose research. Biologists know that the availability of nitrogen can be the limiting factor in reproduction. Nitrogen is an essential part of an animal's diet, and moose get it from fresh, budding leaves. Their diet is low in nitrogen most of the year, so the two months when young leaves are available are critical. Nitrogen deficiency - and resulting protein deficiency - can cause failure to conceive, failure to carry a baby to term and low birth weights.
"Moose can be really productive - twinning rates can be 90 percent, and they will produce triplets. You'll see yearlings being bred," said wildlife biologist Stacy Jenkins. "Or twinning rates drop to 20 percent, and moose will skip years calving, or wait until they are three or four years old to have their first calf."
Jenkins is involved in several nutrition studies. One looks at the comparative nutritional values of cottonwood, birch and willow leaves. Another examines how moose respond to excellent and poor habitat, and how hard moose must work to find food in marginal habitat.
Kenai Moose Research Center director Tom Lohuis wants answers to some of the big questions in moose research today.
"What drives moose reproductive rates - what are the essential nutrients?" he said. "What does it take to grow a moose calf? How many pounds of willow, alder and spruce? I want to understand what it takes to support a moose and keep it healthy, and take that to the population level. Then we'll be able to understand how changes in predator populations, nutritional availability and moose density affect the moose population."